Mechanical lash adjuster



`April 30, 1963 E. A. THOMPSON 3,087,475

MECHANICAL LASH ADJUSTER Filed Aug. 11, 1961 4 Sheets-Sheet 1 IN VEN TOR. ER A. THOMPSON ATTOR/V'y April 30, 1963 E. A. THoMPsQN 3,087,475

MECHANICAL LASH ADJUSTER Filed Aug. 11, 1961 4 Sheets-Sheet 2 IN V EN TOR.

EHRL A 7'AOMPJ`0/V April 30, 1963 E. A. THOMPSON 3,087,475

MECHANICAL LASH ADJUSTER Filed A lg. 1l, 1961 4 Sheets-Sheet 3 INVENTOR. E ARL A. THOMPSON A TTORNEY April 30, 1963 E. A. THOMPSON 3,087,475

MECHANICAL LASH ADJUSTER Filed Aug. 11, 1961 4 Sheets-Sheet 4 m5 tTlll] INVENTOR. EARL A. THOMPSON ATTORNEY United States Patent O 3,087 ,47 MECHANICAL LASH ADJUSTER Earl A. Thompson, 1300 Hilton Road, Ferndale, Mich. Filed Aug. 11, 1961, Ser. N0. 131,714 so Claims. (C1. 12s- 90) This invention relates to lash adjusting mechanism such as is adapted for use with engine valve operating tr-ains. This is acontinuation-in-part of co-pending and now abandoned application S.N. 762,121, tiled September 19, 1958.

The modern high :compression overhead valve type of automotive engine customarily utilizes valve trains of the rocker arm type which valve trains, being `fairly long, are frequently provided 'with automatic lash adjusting devices. Such devices, as heretofore utilized commercially, are almost entirely of the hydraulic type and utilize a chamber of trapped oil which is replenished from the lubricating system through an internal check valve. While these hydraulic valve lifters function quite well for their intended purpose, they do malfunction occasionally due to accumulations of varnish and other oxidation products and are subject to jamming with 'dirt particles which may be circulated through the lubrication system.

The sensitivity of hydraulic valve lifters to varnish and dirt have lead designers to seek improved reliability in automatic lash adjusters through the use of purely mechanical devices. Heretofore, mechanical lash adjusters have been based -upon the use of a force-multiplying mech- -anism, such :as a wedge, eccentric or a helix, all of which are inherently unreliable when utilized at or near their critical Ifriction angle. In prior designs of mechanical lash adjusters it has been necessary to utilize the forcemultiplying device at or near this Iangle and because of the unavoidable small changes in the friction coefcient which arise under various operating conditions they have not proven satisfactory.

IIt is an object of the presen-t invention to provide la mechanical lash adjuster in which a force-multiplying mechanism of the class embracing wedges, cams and screws may be utilized with an angle of inclination whichv is inherently self-locking, that is, an angle which is substantially smaller than the critical friction angle.

A further object of the invention is to provide an improved lash adjusting mechanism of the mechanical type wherein a desired positive increment of potential lash is deliberately introduced into the valve train each time it is under load so that an automatic lash removal device may function as soon as the load is removed. The invention also seeks to accomplish this with positively driven mechanical actuating trains independent of frictional forces.

Further objects and advantages of the present invention will be apparent from the following description, refer-ence being had to the accompanying drawings wherein several forms of t-he pre-sent invention are illustrated.

FIGURE 1 is a top view o-f one form of rocker arm and lash adjuster assembly embodying the present invention, with parts broken away on line 1 1 of FIGURE 2.

FIGURE 2 is a cross `sectional view on line 22 of FIGURE ll.

FIGURE 3 is a cross sectional view on line 3-3 of FIGURE 1.

FIGURE 4 is a developed ldiagram of valve stem travel as compared with push rod travel.

FIGURE 5 is an elevational View of another form of lash adjuster assembly embodying the present invention.

FIGURE 6 is a top view of the assembly shown in FIGURE 5'.

FIGURE 7 is a cross sectional 'view on line 7-7 of FIGURE 6.

` FIGURE `8 is fragmentary cross sectional view to a Patented Apr. 30, 1963 "ice langer scale on line 8-8 of FIGURE 7 with the parts in the valve opened position.

FIGURE 9' is an end elevational view of a diierent engine mounting for the lash adjuster assembly of the present invention.

FIGURE 10 is a side elevational view of a diierent engine mounting .for the lash adjuster assembly of the present invention.

The invention has been illustrated in embodiments suitable for use with -valve trains which employ individually fulcrumed rocker arms. Regarding FIGURES l-3, such valve trains comprise a push rod 10 which is actu-ated from the conventional cam shaft, not shown, and the upper end of which cooperates with a spherical socket formed in one end of a deep drawn or cast rocker arm 12. The rocker arm 12 has '1an upwardly facing spherical socket 14 which rocks upon a spherical fulcrum member 16 and has a nose portion `18 in abutting engagement with the end of a valve stem v20, having the usual yspring 22 and retainer 24. A stud 26 is xed to the engine cylinder head and carries a tapered portion 28 and a threaded portion 30 for the purpose of mounting a self-contained lash adjuster :assembly generally designated 32 which serves to variably position the tfulcrum 16 with respect to the stud 26 in a manner later to be described. The stud 26A may be provided with a lubricant passage 34 through.' which lubricant may be supplied to the interiorjof the- If desired,

lash .adjuster 32 and the rocker arm 12. suitable lubricating passages 36 may be provided to lubricate the abutting contacts of the rocker arm with the push rod and -stem respectively.

The lash adjuster comprises a tubular base 38 which has an internal taper mating with taper 28 and is retained' by |a nut 31 on thread 30 so as to be iixed in'relation to the stud 26 :but nevertheless removable therefrom lfor replacement of t-he entire lash adjuster 32 if required. The base 3-8 is provided 'with external threads 40 which 'have a helix angle `significantly less than the -friction .angle of the particular materials being utilized which are normally -hardened steel. In a typical lash adjuster this angle mayhe of the order of magnitude of 5 degrees and the thread 40 maybe approximately in diameter and comprises a ve element thread, each element havinga pitch of seven threads per inch. Thus, in the sectional view shown,

the thread may :appear to 'be one of 35 threads per inch.`

Shiftable on the base 38 both rotationally and transl-atably is a member `42 having an internal thread match-l ing the thread `40 and having its lower surface abutting the upper surface of the spherical ffulcrum member 16.

A transverse Igroove y44 in the bottom of the member 4-2 provides for passage of oil as Well as for an anchoring point for a helical spring, later to be described. The member 42 has a shoulder 46 against which a cup member 48 rests and is rotatably mounted with respect to member 42.

The cup 48 forms the driving member of a one-way,I

clutch and for this purpose is provided with three or more cam surfaces 50. Cup 48 is provided with a radiallyprojecting arm 52* which'rides in a slot 54 formed in the side wall'of the rocker arm 12 as shown in FIGURES l 1 and 3. The point of engagement between slot 54 and arm 52 is considerably -above the imaginary pivot point of the rocker arm about fulcrum 16 as is evident from FIGURE 3. Above the shoulder 46 Ithe member 42 is:

j tending to advance the fulcrum 1,6 downwardly, by means of a helical spring 62 which is anchored at its lower end in the slot 44 and at its upper end in the cup 48 as shown in FIGURE 2. The spring 62 is chosen to have insufcient strength to turn the member 42 while the valve train is under load but with suicient strength to turn the same when the load is relieved. A conical spring 64 biases the cup or cage 58 clockwise in FIGURE 1 with a light force in order to urge the rollers 56 into the narrow ends of the Vcam slots 50.

The lash adjuster assembly 32 prior to installation is wound up to preload the springs 62 and 64- and is retained in the woundcondition lby means of a temporary lock pin 66 which is engaged in a suitable hole in a plate 68 and a hole in the end of the member 42. Plate 68 may be staked to the upper end of base 38 and provide a suitable hole for anchoring one end of the spring Regarding FIGURES -8, another form of the invention yis illustnated, wherein the valve train similarly comprises a push rod 110 which is also actuated from the conventional cam shaft, not shown, and the upper end of which cooperates with an abutment such as a spherical socket 1211 formed in one end of a deep drawn or cast rocker arm l112. The elongated rocker arm y112 has an upwardly facing semi-spherical socket 114 which rocks upon a semi-spherical faced fulcrum member 116, and -a nose portion 118 in abutting engagement with the end of a valve stem 120 having a spring 122 acting to seat the valve by means of .a retainer 124. An engine member such as -a stud r126 xed to the cylinder head 127 carries a splined portion 128 and a threaded end portion 130 for the purpose of mounting a self-contained lash adjuster assembly generally designated 132 which serves to variably position the rocker arm fulcrum 1'16 with respect to the xed stud 126 in a manner later to be described.

The lash adjuster 132 comprises a tubular base 138 which has internal splines 139 mating with splines 128 on the engine member and is retained by a self-locking nut 131 on threads 130 so as to be axially adjustable in relation to the stud 126, but nevertheless removable therefrom for replacement of the entire lash adjuster 132 if required. The lash adjuster is urged upwardly against the nut 131 by ythe valve spring 122 when the train is loaded, and by the take-up action of the adjuster itself when thel valve is seated. The base 138 is provided with external threads 140 which have a helix angle significantly less than the friction angle of the particular materials being utilized, which are normally hardened steel, and may oomprise a three Hight thread. This force multiplying thread is thus inherently self-locking 'against the load force of the valve train.

Shiftable on the base 138 both rotationally and translatably is a nut or adjusting member `142 having an internal thread 1143 matching the thread 140, and having its lower surface abutting and notationally slidable on the upper surface of the spherical fulcrum member 116. An annular chamber 145 is provided in the lower end of the member 142 to house a lash take-up spring, described below. A nadial slot 144 in the bottom wall of the spring chamber of the member 142 provides an anchoring point for the take-up spring. The member 142 has an external shoulder 146 against which a one-way clutch rests in concentric relationship with respect to the rotary adjusting member 142.

The one-way clutch may comprise a driving member 148 which is provided with six Iaxially extending cam surfaces 150 on the axially unobstructed inner surface thereof. Cup 148 is also provided with a radially projecting actuating arm 152 which rides snugly ina slot 154 formed in .the side wall of the rocker arm 112, as shown in FIG- URES 5-8. The point of engagement between the actuating shoulder of .the slot 154 and arm 152 is considerably above the pivot point of the rocker arm about fulcrum 116, as is evident from FIGURES 5 and 7. Above the shoulder 146 is also provided six clutch rollers 156,

each disposed axially, one adjacent each cam surface for cooperation with a cylindrical surface on the nut 142. The rollers 156 are also spaced by an unlocking member 158 also having a radially projecting actuating arm 160 which cooperates with the same slot 154, but with a lost motion connection and at a greater distance from the rocker arm pivot so as to be in somewhat different time phase than the arm 152. A spring 164 biases the unlocking cage 158 clockwise in FIGURE 8 with a light force in order to urge the rollers 156 into .the narrow ends of the cam slots 150, ready to perform their clutching function; the spring 164 also holds the one-way clutch assembly down against the shoulder 146.

The member 142 is biased rotationally, in a. direction tending to advance the fulcrum 116 downwardly in the direction of decreased lash, by means of a torsion motor 162 of the type wherein flat spring wire is coiled on itself. This spring is too weak to act when the valve train is loaded, and is yanchored at its outer end in the slot 144, and at its inner end is anchored relative yto the engine 127 by means of a slot 163 in the lower end of the base 138, as shown in FIGURE 7. The upper surface of the fulcrum member 116 and the opposed bottom surface of the spring chamber -145 :are dished conically inwardly to make room for the spring 162 as the axial position of the fulcrum shifts relative .to the stud and screw member 138 fixed thereon.

The lash adjuster 'assembly 132 prior to installation is wound up to preload the springs 162 and 164, and may be retained in the wound condition by means of a temporary lock pin 166 which is engaged in a suitable opening in the member 142 and la hole in the member 138, sevenal of which may be provided in each member to facilitate installation locking of the unit with the correct preload.

In FIGURE 4 there is shown by the line 70 a horizontal plot of push rod motion, but showing only the portion of the action when the cam lobe is eifective. The upper line 72 plots the corresponding movements of the valve stem 20 to show the differences which are introduced by the lash adjuster mechanism. It will be seen from FIGURE 4 that the push rod motion and the valve stem motion correspond exactly during the rising portion of the cam ramp and during -the initial part of the falling portion of the cam ramp.

In operation, initial travel of the rocker arm in a clockwise direction on the valve closing stroke picks up the arm 52, 152 (both embodiments function similarly) to rotate it coun-terclockwise in FIGURES 1, 8, tightening the rollers 56, 156 into clutching engagement with their cam slots 50, 150 and the surface of the nut 42, 142. After point 74, the one-way clutch begins to drive the member 42, 142 along lwith the cup 48, 148. This counterclockwise rotation of member 42, 142. causes an upward translation of the member 42, 142 and thus permits the fulcrum 16, 116 to recede upwardly. This motion introduces an increment of potential lash into the valve train.

At a time when a point such as 76 is reached, the wall of slot 54, 154 actuates the arm 69, i160` on cage 58, 158 to unlock the rollers 56, 156 and thereafter no further lash is introduced into the train and the valve Stem follows the motion of the push rod until a point such as 78 is reached where the Ivalve seats. It will be noted that the arm 60, 160 is at a higher point in the slot 54, 154 than is the arm 52, 152 and at this radius the slot walls partake `of a greater travel. Thus the cage member 58, '.158 overtakes the cup 48, 148 at the point 76.

Thus the valve stem comes to rest on its seat earlier than the cam follower and push rod reach the end of their downward travel. This cornes about by reason of lthe fulcrum having been raised a small increment. The spring 62, 162, however, now takes over control of the member 42, 142 since that member is now entirely free of the one-way clutch and the thread locking force of the valve spring. As the push rod receides further, the member 42, 142, is driven clockwise by spring 62, 162 and thus forces the fulcrum downwardly as fast as the recession of the p ush rod will permit, thus precluding any actual lash in the system. The increment of potential lash rwhich was introduced by the one-way clutch becomes wiped out and the parts come to rest with no lash in the system.

If, due to temperature or other changes, there should be need to adjust the datum position of the fulcrum, such Iadjustment requirement adds itself algebraically to the increment of potential lash yand the net sum is wiped out by the action of the last take-up spring. Y 4

It will thus be seen that the present invention provides an improved mechanical lash adjuster in which reliability is assured and which does not depend on wedges, cams or screws having angles close to the friction angle. At the same time all lash-adjusting motions :are produced by positively acting drives independent of any coefficient of friction between two relatively sldable surfaces. That is to say, such ldrives operate through fully compulsive connections to the threaded adjusting members, both as to the actuating connections (e.g., in the rst embodiment: 54--52-48--50--56) -to the nut and as to the reactive connection (e.g., in the first embodiment: 12--10-cylinder head (not shown)26-2831) to the threaded stud.

In FIGURES 9 and l0, a different engine mounting and rocker arm are shown. A push rod 210 is actuated from the cam shaft, no-t shown, and cooperates with a spherical socket 211 formed in one end of a dished rocker arm 212. The rocker arm 212 has an upwardly facing spherical socket 214 which rocks upon the spherical fulcrum of a lash adjuster according to ,this invention. The rocker arm has a nose portion 218 in abutting engagement with the end of a valve stem 220, after the normal fashion. i

Studs 226 are iiXed to the engine cylinder head 227 by a" T shaped bracket 229, which may carry a stud from each arm thereof and may be secured against rotation by a key and way arrangement 23.1 and against upward movement by a'fastener 233. The downwardly extending `studs may support a Ilash adjusting unit by either the wedge taper or spline connection described above. One advantage of such a mounting is the ability to use deep drawn or cast rocker arms including an actuating shoulderl 254 similar to the ones described above yet without necessitating the extra step of providing a stu-d hole in the bottom. v

While the embodiments of the invention herein disclosed constitute preferred forms, it is to be understoody trainjand then completely disengaging the force-multiplying means Well before the load on the train is relieved, and yieldab-le biasing means for precluding actual lash from the `train as the load on the train is relieved.

2. lIn an engine valve operating train, a lash adjusting system of the mechanical type comprising a threaded adjusting mechanism having a self-locking helix angle, mechanical means including a fully compulsive driving connection and a fully compulsive reaction connection to the adjusting mechanism for posi-tively introducing an increment of potential lash into the train while the train is under yload :and a resilient biasing element for removing lash from the train only while the load on the train is relieved.

3. l'In an engine valve `operating train, a lash adjusting 6 system'of the mechanical type comprising a force-multiplying adjusting mechanism of the self-locking type, means including a fully compulsive `driving connection and a -fully compulsive reactive connection with the adjusting mechanism for positively introducing an increment of potential lash into the train While the .train is under load and a resilient biasing element for removing lash from the train only while the load on the train is relieved.

4. A mechanical lash adjuster `for an intermittently loaded motion transfer train comprising a pair of relatively shiftable adjusting members havin-g a force multiplying engagement with each Iother to vary the efective length of the train and inherently self-locking against the intermittent load force of the train, iirst means responsive to transfer train motion for positively shifting one of the adjusting members relative to the other adjusting member in .the direction of increased lash each time the train is loaded to introduce an increment of potential lash, second means having insuilicient force to operate the one adjusting member while the train is loaded for biasing the one adjusting member relative to the other adjusting member in the direction tof .decreased lash as in intermittent `load on the train is relieved to wipe out the potential lash introduced by the first means plus or minus any required adjustment, `and means securing the other adjusting member against shifting relative to the one member yin a direction which would vary the eiective length of .the trai-n.

. 5. A mechanical lash adjuster for an intermittently loaded motion transfer train comprising a pair of relatively shiftable adjusting members having a force multiplying engagement with each other to vary the effective length of the .train and inherently self-locking against the .intermittent load force of the train, first means including a one-way drive arrangement responsive to transfer train motion for positively shifting one Iof the adjusting members relative to the other -adjusting mernber in the direction of increased lash each time the train is loaded to introduce 4an increment ofpotential lash, second meansl including a mechanical spring arrangement having insufficient force to operate -t-he one adjusting member while the train is loaded for biasing the one adju-sting member relative to the other adjusting member in the direction of decreased lash as the intermittent loa-d on the train is relieved to wipe out the potential lash introduced by the lirst means plus or minus any requiredadjustment, and means securing the other adjusting member against shifting relative to the Ione member in a direction which would vary the effective length of .the train.

6. A mechanical lash -adjuster'for an intermittently loaded, reciprocating, motion transfer train comprising a palr of relatively shiftable adjusting members'having a force multiplying engagement with each other to vary .the eiective length of the :train in response to lsuch relat1ve shlftlng and inherently self-locking against shifting in response to load force imposed in the line of motion transmitted by the train, an :actuating means for shiftingV one yof said members relative to the other lto` produce an increment 4of potential lash while the train is under load, said actuating means including 'a self-locking one-way grippmg device for driving one of the adjusting members, means for positively constraining .the other adjusting member against conjoint motion in the same direction,A

a releasing means for disengaging the one-way gripping devlce to terminate the relative shifting of the adjusting members while the train continues under load, and resilient means having insutlicient force to operate said members while under load and acting in the opposite direction to .the actuating means whereby the increment of potential lash is removed land any compensating adjustment in' the effective length of the Itrain is introduced as the load is relieved from the train.

' 7. An engine valve train comprising a threaded lash adjusting member having a helix :angle inherently selflocking against the thrust of valve actuation, an actuator responsive to valve train motion` and including a selflocking one-way gripping device connected to turn the adjusting member while the train is under load in a direction to introduce .an increment of potential lash into the train, a releasing device also responsive tot valve train motion and arranged to disengage lthe gripping device at a subsequent time in the operating cycle, and resilient means for turning fthe adjusting member in the opposite direction to wipe out the lash in the train while the load is relieved.

8. An engine valve train comprising a vthreaded lash adjusting member having a helix angle inherently selflocking against the thrust of Valve actuation, an actu-ator responsive to valve train motion and including a means for positively engaging and then positively disengaging the adjusting member to turn the adjusting member a predetermined distance in the lash increasing direction while the -tr-ain is under load, and resilient means for turning the adjusting member in the opposite direction to wipe out Ithe lash in the :train while the load is relieved.

9. A valve operating train comprising a pair `of threaded members relatively rotatable to vary `the lash in the train, a biasing spring connected between the members to rurge them in the direction of decreased lash and having insuicient force to overcome the operating load on the train, and means forming a compulsive connection between said members -for producing relative threading motion in a lash increasing direction while the train is under load.

l0. A valve operating train comprising a pair of threaded members relatively rotatable to vary the lash in the train, a biasing spring connected between the members to urge themv in the direction of decreased lash and having insufficient force to overcome the operating load on the train, and means including a one-way gripping device actuated by motion of the valve train and forming a compulsive connection between said members for producing relative threading motion in a lash increasing direction while the train is under load.

11. A valve oper-ating train comprising a pair of threaded members relatively rotatable to vary the lash in the train, ya biasing spring connected between the members to urge them in the direction of decreased lash and having insufficient force to overcome the operating -load on ythe train, a one-way gripping device associated with said members for producing relative threading motion in a lash increasing direction and means for releasing said device while the train is under load.

12. A mechanical lash adjuster for an intermittently loaded motion transfer train comprising a base, a member shiftable relative thereto to increase or decrease lash, means including a self-locking force-multiplying mechanism for shifting said member, resilient means for operating said mechanism in -a direction to decrease lash and having insuicient force to operate the lash adjuster While the adjuster is under load, and positive mechanical drive means including a clutch engageable with said mechanism and means for disengaging the clutch while the adjuster is under load for operating said mechanism a predetermined distance in a direction to increase lash whereby an increment of potential lash is introduced during loaded operation of the train and that increment, plus or minus -any required adjustment, is removed by the resilient means when the load is relieved.

13. A mechanical lash adjuster for an intermittently loaded motion transfer train comprising a base, a member shiftable relative thereto to increase or decrease lash, means including a self-locking screw mechanism for shifting said member, resilient means for operating said mechanism in a direction to decrease lash and having insufficient force to operate the lash adjuster while the adjuster is under load and positive mechanical drive means effective while the adjuster is under load including fully compulsive driving and reactive connections for operating said mechanism in a direction to increase lash whereby an increment of potential lash is introduced `during loaded operation of the train and that increment, plus or minus any required adjustment, is removed when the load is relieved.

14. A mechanical lash adjuster for an intermittently loaded motion transfer train comprising a base, a member shiftable relative thereto to increase or decrease lash, means including a self-locking force-multiplying mechanism for shifting said member, a biasing spring for operating said mechanism in a direction to decrease lash and having insufficient force to operate the lash adjuster while the adjuster is under load and positive mechanical drive means engaged and positively disengaged while the adjuster is under load `for operating said mechanism a predetermined distance in a direction to increase lash whereyby an increment of potential lash is introduced during loaded operation of the train and that increment, plus or minus any required adjustment, is removed by the biasing spring when the load is relieved.

15. A mechanical lash adjuster for an intermittently loaded motion transfer train comprising a base, a member shiftable relative thereto to increase or decrease lash, means including a self-locking force-multiplying mechanism for shifting said member, resilient means for operating said mechanism in a direction to decrease lash and having insufficient force to operate the lash adjuster while the adjuster is under load, fully compulsive means connecting the motion transfer train to positively operate said mechanism in a direction to increase lash, and means for disconnecting said fully compulsive means before the load is relieved from the train whereby an increment of potential lash is introduced during loaded operation of the train and that increment, plus or minus any required adjustment, is removed by the resilient means when the load is relieved.

16. A mechanical lash adjuster for an intermittently loaded motion transfer train comprising a base, a member shiftable relative thereto to increase or decrease lash, means including a self-locking screw mechanism for shifting said member, resilient means for operating said mechanism in a direction to decrease lash and having insui'hcient force to operate the lash adjuster while the adjuster is under load and a one-way clutch and fully compulsive driving and reactive connections with the motion transfer train to operate said mechanism in a Vdirection to increase lash whereby an increment of potential lash is introduced during loaded operation of the train and that increment, plus or minus any required adjustment, is removed by the resilient means when the load is relieved.

17. A mechanical lash adjuster for an engine valve train comprising a base, a member shiftable relative thereto to increase or decrease lash, a self-locking force-multiplying mechanism for shifting said member, resilient biasing means for operating said mechanism in a direction to decrease lash whenever the valve train is relieved of load and positive mechanical drive means having fully compulsive driving and reactive connections with said mechanism to introduce an increment of potential lash while the valve train is loaded whereby that increment, plus or minus any required adjustment, may be removed by the biasing means when the load is relieved.

18. A mechanical lash adjuster for an engine valve train comprising a base, a member shiftable relative thereto to increase or decrease lash, a self-locking screw mechanism for shifting said member, resilient biasing means for operating said mechanism in a direction to decrease lash whenever the valve train is relieved of load and positive mechanical -drive means having fully compulsive driving and reactive connections with said mechanism to introduce an increment of potential lash while the valve train is loaded whereby that increment, plus or minus any required adjustment, may be removed by the biasing means when the load is relieved.

19. A rocker arm for the valve gear of an internal combustion engine comprising an elongated trough shaped member having a fulcrum journal intermediate its ends, means forming a pair of abutments adjacent each its ends for engaging a push rod and a valve stem, respectively, and means including an actuating shoulder on the arm forming a third abutment for positively operating the one- Way drive arrangement of a spring-loaded mechanical lash adjusting unit, the actuating shoulder lying away from the fulcrum center for oscillatory movement about the fulcrum center.

20. A rocker arm forthe valve gear of an internal combustion engine comprising an elongated trough shaped member having a depression in its bottom wall containing a fulcrum journal intermediate its ends, means forming external abutment surfaces adjacent each end, said arm having a trough wall which extends radially outwardly from the fulcrum center a substantial distance, and means including a shoulder on the radially extending wall forming a third abutment sur-face for actuating a lash adjuster and lying away from the fulcrum center for oscillatory movement about the fulcrumv center.

21. A unitary rocker arm for the valve gear of an internal combustion engine comprising an elongated trough shaped member having a downward depression in its bottom wall containing a fulcrum journal intermediate its ends, means forming external abutment surfaces on its bottom wall adjacent each end, said arm having trough side walls which extend upwardly from -the fulcrum center a substantial distance, and means forming a third abutment surface for actuating a lash adjuster and facing approximately at right angles to the other abutment surfaces, said means including an opening Iin the side wall lying above and a-t one side of the fulcrum center for oscillatory movement about the fulcrum center.

22. In an engine valve operating train having a rocker arm mounted 'for rocking about a fulcrum, a lash ladjusting system comprising a unitary assembly providing the fulcrum and comprising a base, a member shiftable relative thereto to advance and retract the fulcrum, means including `a self-locking force-multiplying mechanism for shifting said member, resilient means for operating said mechanism in a direction to advance the fulcrum and having insuflicient force to operate the mechanism while the valve train is under load, and means associated with the rocker arm to positively operate the mechanism in the direction to retract the fulcrum while under load whereby an increment of potential -lash is introduced during loaded operation of the train and that increment, plus or minus any required adjustment, is removed byV the resilient means when the load is relieved.

23. In an engine valve `operating .train having a rocker arm mounted for rocking about a fulcrum, a lash adjusting system comprising a unitary assembly providing the fulcrum and comprising a base, a member rotatable and translatable relative thereto to advance and retract the fulcrum, means including a self-locking screw mechanism for translating said member, resilient means for operating said mechanism in a direction to advance the fulcrum and having insufficient force to operate the mechanism `while the valve train is under load, and means including one-way drive means associated with the rocker `arm to positively operate the mechanism in the direction to retract the fulcrum while under load whereby an increment of potential lash is introduced during loaded operation of the train land that increment, plus or minus any required adjustment, is removed bythe resilient means when the load is relieved.

24. In Aan eninge valve operating train having a rocker arm mounted for rocking about a fulcrum, a lash adjusting system comprising a unitary assembly providing the fulcrum and comprising a base, a member rotatable and translatable relative thereto to advance and retract the fulcrum, means including a self-locking screw mechanism for translating said member, resilient means for operating said mechanism in a direction to advance the fulcrum and having insuficient force to operate the mechanism while the valve train is under load, and means including a one-way clutch associated with the rocker arm to positively operate the mechanism in the direction to retract the fulcrum -while under load whereby an increment of potential lash is introduced during loaded operation of the train and .that increment, plus or minus any required adjustment, is removed by the resilient means when the load is relieved, said one-way clutch being arranged to drive the screw mechanism during valve closing movement of the train, yand additional means associated with the rocker arm for releasing the one-way clutch prior to the end of such movement.

25. In an engine valve operating train having `a rocker yarm mounted vfor rocking about a fulcrum, a lash adjusting system comprising a unitary assembly providing the fulcrum and comprising a base, means for removably mounting the base in fixed relation tothe engine, a member shiftable relative thereto to advance and retract the fulcrum, means including `a self-locking force-multiplying mechanism for shifting said member, resilient means for operating said mechanism in a direction to advance the fulcrum and having insuicient force to operate the mechanism while the valve train is under load, and means including one-way drive means associated with the rocker arm to positively operate the mechanism in the direction to retract the fulcrum while under load whereby an increment of potential lash is introduced during loaded operation of the train and that increment, plus or minus any required adjustment, is removed by the resilient means when the load is relieved.

26. A mechanical lash adjuster comprising a self-locking force-multiplying member rotatable to adjust the amount of lash, biasing means connected with the member to urge it in the direction of decreased lash, and one- Way clutch means connected with the member for producing motion in the direction ofincreased lash including a clutch driving member in juxtaposed concentric relationship to the force-multiplying member, the juxtaposed surface of lone of the members having a plurality of one- .way gripping cams formed thereon, a rollable clutching element wedgingly associated with each cam to transfer motion of the driving member to the force-multiplying member in only the rotational direction of increased lash, and element releasing means connected to move each clutching element out of operative association with its cam so that the biasing means may function.

27. A mechanical lash adjuster comprising a self-locking force-multiplying member rotatable to adjus-t the amount of lash, biasing means connected with the member to urge it in the direction of Vdecreased lash, and onerway clu-tch means connected with the member for producing motion in the direction of increased lash includ- -ing a clutch driving member in juxtaposed concentric re Ilationship to the force-multiplying member, the juxtaposed surface of one of the members having a plurality of axially extending one-way gripping undulations formed thereon, the latter member being free tfrom interfering ledges at both axial ends `of the juxtaposed surface to facilitate formation of the undulations thereon, and means Vfor releasing the one-way clutch means so tha-t the biasing means may function.

28. A mechanical lash adjuster for an intermittently loaded motion transfer train shiftable relative to an engine member comprising a pair of cooperating adjusting members having mating self-locking helix angle surfaces, one-way drive means responsive to transfer train motion to positively rotate one of the adjusting members in the direction of increased lash when the train is under load, locking means -securing the other of the adjusting members against rotation relative to the engine member, and a coiled spring connected at one end directly with one member and at the other end directly with the other member to bias the one member in the direction of decreased lash when the load on the train is relieved.

29. A mechanical lash adjuster for an intermittently loaded motion transfer train shiftable relative to an engine member comprising a pair of cooperating adjusting members having mating-Self-locking helix angle Surfaces, one-way drive means responsive to transfer train motion to positively rotate one of the adjusting members in the direction of increased lash when the train is under load, locking means securing the other of the adjusting members against rotation relative to the engine member, and torque biasing means connected to urge the one member in the direction of decreased lash when the load on the train is relieved including a spirally wound length of at spring steel connected at one end with the one member and anchored at the other end to the engine member.

30. A mechanical lash adjuster for an intermittently loaded motion transfer train shiftable relative to an engine member comprising a pair of cooperating adjusting members having mating self-locking helix angle surfaces, rst means responsive to transfer train motion to positively rotate one of the adjusting members in the direction of 20 increased lash when the train is under load, second means connected with the one member to bias it in the direction of decreased lash when the load on the train is relieved, and means securing the other of the adjusting members against rotation relative to the engine member including an axially extending aperture in one of the members having a non-circular cross sectional configuration, and a stud on the other `of the members of similar shape designed to be slidably received within the aperture to a varying axial extent whereby the first or the second means may rotate the -one adjusting member while the other adjusting member is held in non-rotative relationship to the engine member.

References Cited in the le of this patent UNITED STATES PATENTS 1,707,749 Almen Apr. 2, 1929 1,948,063 Burkhardt Feb. 20, 1934 1,979,348 Russell Nov. 6, 1934 2,131,507 Goodwin Sept. 27, 1938 2,743,715 Randol May 1, 1956 2,845,053 Humphreys July 29, 1958 2,962,011 Rosenberger Nov. 29, 1960 3,009,450 Engemann Nov. 21, 1961 

12. A MECHANICAL LASH ADJUSTER FOR AN INTERMITTENTLY LOADED MOTION TRANSFER TRAIN COMPRISING A BASE, A MEMBER SHIFTABLE RELATIVE THERETO TO INCREASE OR DECREASE LASH, MEANS INCLUDING A SELF-LOCKING FORCE-MULTIPLYING MECHANISM FOR SHIFTING SAID MEMBER, RESILIENT MEANS FOR OPERATING SAID MECHANISM IN A DIRECTION TO DECREASE LASH AND HAVING INSUFFICIENT FORCE TO OPERATE THE LASH ADJUSTER WHILE THE ADJUSTER IS UNDER LOAD, AND POSITIVE MECHANICAL DRIVE MEANS INCLUDING A CLUTCH ENGAGEABLE WITH SAID MECHANISM AND MEANS FOR DISENGAGING THE CLUTCH WHILE THE ADJUSTER IS UNDER LOAD FOR OPERATING SAID MECHANISM A PREDETERMINED DISTANCE IN A DIRECTION TO INCREASE LASH WHEREBY AN INCREMENT OF POTENTIAL LASH IS INTRODUCED DURING LOADED OPERATION OF THE TRAIN AND THAT INCREMENT, PLUS OR MINUS ANY REQUIRED ADJUSTMENT, IS REMOVED BY THE RESILIENT MEANS WHEN THE LOAD IS RELIEVED. 